Analysis of docosanol using GC/MS:Method development,validation,and application to ex vivo human skin permeation studies

Docosanol is the only US Food and Drug Administration(FDA)approved over-the-counter topical product for treating recurrent oral-facial herpes simplex labialis.Validated analytical methods for docosanol are required to demonstrate the bioequivalence of docosanol topical products.A gas chromatography/selected ion monitoring mode mass spectrometry(GC/SIM-MS)method was developed and validated for docosanol determination in biological samples.Docosanol and isopropyl palmitate(internal standard)were separated on a high-polarity GC capillary column with(88%cyanopropy)aryl-polysiloxane employed as the stationary phase.The ions of m/z 83 and 256 were selected to monitor docosanol and isopropyl palmitate,respectively;the total run time was 20 min.The GC/SIM-MS method was validated in accordance with US FDA guidelines,and the results met the US FDA acceptance criteria.The docosanol calibration standards were linear in the 100-10000 ng/mL concentration range(R^(2)>0.994).The recoveries for docosanol from the receptor fluid and skin homogenates were>93.2%and>95.8%,respectively.The validated method was successfully applied to analyze ex vivo human cadaver skin permeation samples.On applying Abreva®cream tube and Abreva®cream pump,the amount of docosanol that penetrated human cadaver skin at 48 h was 21.5±7.01 and 24.0±6.95 ng/mg,respectively.Accordingly,we concluded that the validated GC/SIM-MS was sensitive,specific,and suitable for quantifying docosanol as a quality control tool.This method can be used for routine analysis as a costeffective alternative to other techniques.

Effect of the glyceryl monooleate-based lyotropic phases on skin permeation using in vitro diffusion and skin imaging

Glyceryl monooleate(GMO)is a polar lipid that can exist in various liquid crystalline phases in the presence of different amounts of water.It is regarded as a permeation enhancer due to its amphiphilic property.Various phases of GMO/solvent system containing sodium fluorescein were prepared to compare permeability using confocal laser scanning microscopy(CLSM).GMO was melted in a vial in a water bath heated to 45℃.Propylene glycol and hexanediol were homogeneously dissolved in the melted GMO.Sodium fluorescein in aqueous solution was diluted to various ratios and thoroughly mixed by an ultrasonic homogenizer.Each GMO/Solvent system with fluorescein was applied onto the epidermal side of excised pig skin and incubated overnight.CLSM was performed to observe how the GMO/solvent system in its different phases affect skin permeability.Cubic and lamellar phase formulations enhanced the fluorescein permeation through the stratum corneum.A solution system had the weakest permeability compared to the other two phases.Due to the amphiphilic nature of GMO,cubic and lamellar phases might reduce the barrier function of stratum corneum which was observed by CLSM as fluorescein accumulated in the dermis.Based on the results,the glyceryl monooleate lyotropic mixtures could be applied to enhance skin permeation in various topical and transdermal formulations.

Influence of chemical penetration enhancers on skin permeability of ellagic acid-loaded niosomes

This study aimed to develop niosomes of ellagic acid(EA),a potent antioxidant phytochemical substance,for dermal delivery and to investigate the influence of chemical penetration enhancers on the physicochemical properties of EA-loaded niosomes.The EA niosomes were prepared by reverse phase evaporation method using Span 60,Tween 60 and cholesterol as vesicle forming agents and Solulan C24 as a steric stabilizer.Polyethylene glycol 400(PEG)was used as a solubilizer while dimethylsulfoxide(DMSO)or Nmethyl-2-pyrrolidone(NMP)was used as a skin penetration enhancer.It was found that the mean particle sizes of EA-loaded niosomes were in the range of 312e402 nm with PI values of lower than 0.4.The niosomes were determined to be spherical multilamellar vesicles as observed by transmission electron microscope and optical microscopy.All niosomes were stable after 4 months storage at 4
C.In vitro skin permeation through human epidermis revealed that the skin enhancers affected the penetration of EA from the niosomes at 24 h.The DMSO niosomes showed the highest EA amount in epidermis;whereas the NMP niosomes had the highest EA amount in the acceptor medium.Concomitantly,the skin distribution by confocal laser scanning microscopy showed the high fluorescence intensity of the DMSO niosomes and NMP niosomes at a penetration depth of between 30e90 mm(the epidermis layer)and 90e120 mm(the dermis layer)under the skin,respectively.From the results,it can be concluded that the DMSO niosomes are suitable for epidermis delivery of EA while the NMP niosomes can be used for dermis delivery of EA.

Investigating the potential of essential oils as penetration enhancer for transdermal losartan delivery: Effectiveness and mechanism of action

The effect of tea tree oil(TTO),cumin oil(CO),rose oil(RO)and aloe vera oil(AVO)on the skin permeation of losartan potassium(LP)was investigated.In vitro skin permeation studies were carried out using rat skin.The mechanism of skin permeation enhancement of LP by essential oils treatment was evaluated by FTIR,DSC,activation energy measurement and histopathological examination.Both concurrent ethanol/enhancer treatment and neat enhancer pretreatment of rat SC with all the oils produced significance increase in the LP flux over the control.The effectiveness of the oils as the penetration enhancers was found to be in the following descending order:AVO>RO>CO>TTO.However,only AVO was the only enhancer to provide target flux required to deliver the therapeutic transdermal dose of LP.FTIR and DSC spectra of the enhancer treated SC indicated that TTO,CO,RO and AVO increased the LP permeation by extraction of SC lipids.The results of thermodynamic studies and histopathological examination of AVO treated SC suggested additional mechanisms for AVO facilitated permeation i.e.transient reduction in barrier resistance of SC and intracellular transport by dekeratinization of corneocytes which may be attributed to the presence of triglycerides as constituents of AVO.It is feasible to deliver therapeutically effective dose of LP via transdermal route using AVO as penetration enhancer.